1. Field of the Invention
The present invention relates generally to surgical instruments and, more particularly, to improved Kerrison type rongeurs for cutting or sampling bone, cartilage and soft tissue.
2. Description of the Background
Rongeurs and similar surgical tools have been known and employed by surgeons for gouging away bone and remove tissue or any other biological material (collectively tissue) during surgical operation. Kerrison type rongeurs are used during spinal surgery to remove bone, cartilage and soft tissue from the spinal posterior in order to gain access into the spinal canal. Such rongeurs typically have a moveable jaw that closes against a stationary anvil or foot plate. In use, a surgeon places bone to be cut between the jaw and foot plate, and squeezes the handle of the rongeur to advance the jaw through the bone to the foot plate, thereby amputating that portion of bone. Typically, the foot plate is flat and the jaw is provided with peripheral cutting edges that bear directly against the flat foot plate at completion of the cutting motion. This guillotine type cutting mechanism, however, has inherent deficiencies. For example, the compression-type cut often results in splintering or fragmentation of the bone which may be lost or dispersed into the surgical site. Additionally, the removed bone or tissue is compacted into jaw, potentially jamming the mechanism of the jaw preventing further motion becoming extremely difficult to remove after each cut. These and other issues with the traditional design have led to numerous alternative approaches to rongeur design.
For example, published U.S. Patent Application No. 2008/0221383 by Bryce Way et al. published Sep. 11, 2008, discloses a tissue excision device comprising a tubular cutting member having a cutting edge at its upper distal end. The tubular cutting member slidably receives a tissue/bone capture member. Near the distal end of the tissue capture member is a radial recess defined by a distal shoulder. In use, the tissue capture member proximally slides within the tubular cutting member, and the top edge of the distal shoulder and the cutting edge of the cutting member, in combination, shear the tissue placed within the recess.
Published U.S. Patent Application No. 2007/0265633 by Jon Kenneth Moon et al. published Nov. 15, 2007, shows a device for removing nucleus pulposus. The device comprises a hollow cutting tube having a cutting edge at its distal end. Reciprocally mounted within the cutting tube is a cylindrical collection tube having an aperture proximate to its distal end. The periphery of the aperture is a cutting edge. In use, the device is positioned so that the nucleus pulposus is inserted within the aperture. The cutting tube then slides over the aperture shearing the nucleus pulposus between the cutting tube's cutting edge and the aperture's periphery.
Published U.S. Patent Application 2005/0267503 by David L. Hunstad published Dec. 1, 2005, teaches a rongeur comprising a base and a slidably connected barrel. At the distal end of the base is footplate, and extending proximally from the footplate is a plunger. The barrel defines a hollow chamber. The plunger is shaped to closely fit within the chamber's opening, and the plunger has sharpened peripheral edges. In use, the barrel is distally advanced so that the chamber receives the plunger, thereby shearing the tissue there between.
U.S. Pat. No. 6,478,805 to James F. Marino at al. issued Nov. 12, 2002, shows a device for removing cut tissue comprising a stationary tubular barrel having an aperture proximate to its distal end. Reciprocally mounted within the stationary tubular barrel is a tubular cutting element with a cutting edge around the distal circumference. To sever tissue, the tissue is inserted within the aperture, and the tubular cutting element is advanced in the distal direction. The cutting element's leading edge shears the tissue against the aperture's periphery.
U.S. Pat. No. 5,582,618 to Albert K. Chin et al. issued Dec. 10, 1996, discloses a rongeur having a fixed inner cutting member terminating with a foot plate at the distal end. The upper, proximal edge of the foot plate comprises a cutting edge. Enclosing the inner cutting member is an outer, tubular cutting member, which has a cutting edge at is distal end. In operation, the outer cutting member translates forward to cover the foot plate, and in the process, the tissue is sheared. The footplate is shaped and dimensioned to closely fit within the opening of the outer tubular member so as to shear tissue placed between the distal end of the outer cutting member and the foot plate.
U.S. Pat. No. 4,777,948 to David W. Wright issued Oct. 18, 1988, shows a rongeur comprising a fixed tubular barrel and cutting element having a cutting edge at its distal end. Slidably mounted within the barrel and cutting element is a rod member. Near the distal end, the rod member has a recess that forms a distal shoulder. In use, the rod member is drawn into the barrel, which shears the tissue by trapping the tissue between the distal shoulder and the cutting edge on the cutting element.
U.S. Pat. No. 3,507,284 to Leonard Simmons et al. issued Apr. 21, 1970, teaches a surgical bone cutter comprising a flat fix blade bar. At the distal end of the fix blade bar is a cutting area having an aperture. The periphery of the aperture is interrupted by a cut-away portion that extends from the outer edge of the blade bar to the inner periphery of the aperture. The inner periphery of the aperture has a cutting edge. Reciprocally mounted flush with the fixed blade bar is a movable cutting blade bar. At the distal end of the blade bar is a concave recess. The contour of the recess serves as a cutting edge. In operation, the bone is slide through the cut-away portion into the aperture. The movable blade bar is slid over the aperture, shearing the bone between the blade bar's concave cutting edge and the aperture's cutting edge.
Despite the foregoing, there remains a need for a Kerrison type rongeur that is capable of cutting bone and tissue by a shearing action to avert the problems associated with conventionally designed rongeurs. Such shearing type cutters would include an edge that passes in close and overlapping proximity to the footplate, thereby giving a scissoring effect and resulting in a cleaner cut.